511   def entityIterator(self, queryGen, batchSize = 100):

   512     """Iterator that yields an entity in batches.

   513 

   514     Args:

   515       queryGen: should return a Query object

   516       batchSize: how many entities to retrieve in one datastore call

   517 

   518     Retrieved from http://tinyurl.com/d887ll (AppEngine cookbook).

   519     """

   520 

   521      # AppEngine will not fetch more than 1000 results

   522     batchSize = min(batchSize,1000)

   523 

   524     done = False

   525     count = 0

   526     key = None

   527 

   528     while not done:

   529       query = queryGen()

   530       if key:

   531         query.filter("__key__ > ",key)

   532       results = query.fetch(batchSize)

   533       for result in results:

   534         count += 1

   535         yield result

   536       if batchSize > len(results):

   537         done = True

   538       else:

   539         key = results[-1].key()

   540